Search

The total cross sections of the 12C+16O fusion have been experimentally determined at low energies to investigate the role of this reaction during late stellar evolution burning phases. A high-intensity oxygen beam was produced by the 5MV pelletron accelerator at the University of Notre Dame impinging on a thick ultra-pure graphite target. Protons and γ-rays were measured simultaneously in the center-of-mass energy range from 3.64 to 5.01 MeV, using strip silicon and HPGe detectors. Statistical model calculations were employed to interpret the experimental results. A new broad resonance-like structure is observed for the 12C+16O reaction, and a decreasing trend of its S-factor towards low energies is found. [ABSTRACT FROM AUTHOR]

A small fraction of presolar SiC grains is suggested to have been formed in the ejecta of classical novae. The Si isotopic abundances in such grains can be determined from the 29P(p,γ)30S reaction rate at nova temperatures. The Si isotopic abundances provide us with information on the nature of the probable white dwarf progenitor’s core, as well as the peak temperatures achieved during nova outbursts, and thus the nova nucleosynthetic path. The 29P(p,γ)30S reaction rate at nova temperatures is determined by two low-lying 3+ and 2+ resonances above the proton threshold at 4399 keV in 30S. However, only one of these two states has only been observed very recently. We have studied the 30S nuclear structure via the 32S(p,t)30S reaction at 5 laboratory angles between 9° to 62°. We have observed 14 states, eleven of which are above the proton threshold, including two levels at 4692.7±4.5 keV and 4813.8±3.4 keV that are candidates for the 3+ and the previously “missing” 2+ state, respectively. [ABSTRACT FROM AUTHOR]